The industrial development of transparent conducting coatings by a Sol-Gel route

By Alec Gordon Gunner

Abstract

Transparent conducting coatings are used in a wide range of applications, particularly displays and photovoltaic devices, and demand is anticipated to increase with the rise of plastic electronics. Indium tin oxide, deposited by sputter coating, is widely used. Concerns over the cost and long term availability of indium, together with environmental concerns over production, are driving a search for more efficient deposition methods and alternative materials. This work represented the early stage development of industrially applicable coatings, hence the work was performed with a supply chain partnership to facilitate commercial uptake. Sol-gel technology was used to facilitate direct printing of patterned layers. Precursors were selected and a processing route developed. Values for glass transition and crystallization temperature were found to be considerably lower than the accepted bulk value. Dip-coated parts yielded indium tin oxide coatings with transparency of 98% and resistivity of 1.5x10\(^-\)\(^2\)\(\Omega\)cm fired in nitrogen and 98% transparency, 3.0x10\(^-\)\(^2\)\(\Omega\)cm resistivity fired in air. A printed coating was produced with 93% transparency and 7.0\(\Omega\)cm resistivity. It was established that the limitations to conductivity arose from low film thickness and lack of macro-scale connectivity within the layer. Initial work was also conducted in preparing tin oxide and silicon-doped zinc oxide coatings